Diagnostics for mechanical heating in star-forming galaxies

In this thesis the molecular emission of species such as CO, HCN and HNC and HCO+ are used to probe and quantify mechanical heating in star-forming galaxies. In the first part of the thesis photo-dissociation models are used to find a diagnostic of mechanical heating at the level of molecular clouds. It was shown that mechanical heating leaves a strong signature in diagnostics that involve high-J to low-J transitions. In the second part of the thesis , synthetic line emission maps of molecular species are computed for model star-forming galaxies. The emission from these maps are used as input to photo-dissociation models in-order to constrain the physical properties, such as gas density and visual extinction, of star-forming galaxies. It was demonstrated that it is essential to consider mechanical heating in modelling the emission of star-forming galaxies using photo-dominated models.